High Performance Shaft Rocker Arm Systems For All Popular Cylinder Heads

Frequently Asked Questions About T&D Shaft Rockers

T&D has compiled a list of the questions most frequently asked our tech staff. However, if there’s a subject not covered that you’d like information on, please send us an e-mail at info@tdmach.com or call 775-884-2292 for personalized assistance.

Actually, virtually every set that goes out the door is a custom set, given the many options for ratios and offsets available. However, we also offer customers full engineering to design and build rocker arms to fit a wide variety of configurations. We cannot say an immediate “Yes” to every request due to the heavy load in engineering, nor can we say, “If its got rocker arms we can build them.” But, given time, we have built rocker arms for some pretty obscure engines, including Ardun, Desoto, Lycoming and Polaris.

T&D has a free inspection process. You pay freight roundtrip. We take everything apart, then inspect, measure and advise. After millions of cycles, aluminum goes beyond its useful life.

In the case of your rockers, they may only need to have a few bearings replaced. But, they may need to be rebodied, while using the old bearings, axles, tips, etc. It all depends on their use, abuse, age, etc. Or, possibly you over-revved and put a valve into a piston. It is possible that just one or two rocker bodies might need to be replaced.

If you suspect anything, even the age of your rocker system, return them for a full inspection. It is best to let the sales department know that your rockers are headed this way but not a requirement. Make sure to enclose pertinent information and just what you want done. Again, it is a free service from T&D.

Unfortunately, we don’t recommend this practice. At first, you are sure to think that we just want to make more money and want you to buy a new set but that is not the case. Weekly, we hear sob stories of people that buy what looks like a really good deal on the surface, but by the time the rockers are adapted to their combination they have invested more time and money than if they’d purchased a new set that is designed to fit their cylinder head and application. Just because the rockers are for a small block Chevy/Ford/Dodge, does not mean they are harmonious with every configuration.

Plus, there is absolutely no way to tell just how used or abused a set of rockers is. Ask yourself, would I buy a set of used aluminum connecting rods? Same material, same answer. No.

Often, we hear from a guy who has gotten a real deal on a set of rocker arms from a NASCAR “cup” team – often in the range of $250. And, we’ll tell you the truth, those rockers are the finest money could buy when the set was designed, machined and shipped. But, they are also quite proprietary so they need the cylinder head that went underneath them. We’re sure that a good engine builder can figure out a piston and pushrod length to match up a “cup” head and rocker set to a compatible block. But just a warning, it might not be the easiest process for a novice.

So, while some components can be purchased used in the on-line swap meet of your choice, we don’t recommend this practice for T&D rockers arms.

Every effort is made to include all necessary components for each rocker arm set. But, you might lose an adjuster nut or hold down stud under the bench. We’re happy to help you get your assembly back up to 100%. Just contact our technical department.

Most of the basic instruction sheets can be found on this website. There may not be one for your exact assembly or part number, but similar engine types can use a generic instruction sheet (i.e. most big block Chevys assemble exactly the same). If the one you need for your particular application cannot be found here, please contact our technical department and one will be provided.

We never recommend turning the adjuster more than 2-1/2 turns down. Pushrod length is determined by the following: (1) Turn the adjuster all the way up into the recess in the rocker body until it stops. (2) Turn the adjuster down one full rotation. (3) This is the initial adjuster position. (4) Once the engine is fully assembled, this will be the starting position where lash will be set, and the adjuster should NEVER be turned one full turn either up or down. For general information, the hole in the adjuster that feeds oil to the pushrod cup shuts off flow completely when the adjuster goes just past two turns down from the initial adjuster position.

Yes, most T&D rocker bodies (except SportComp) have oil passages that enable engine oil to constantly pressurize the trunion bearings and the rocker tips. This feature gives a longevity factor to T&D rockers that the competition does not provide. It also cools the bearings and shafts. There is also an orifice in the adjuster screw that maintains oil to the interface between adjuster cup and pushrod end. This part of the oil passage must remain open and precautions must be taken to maintain adjuster position (another reason that pushrod length is critical).
The rocker arm should not be operated with the adjuster screw more than one turn up or down, from the initial adjuster position. Doing so will cut off the flow of oil to the rocker arm.

Once again, the instruction sheet is your best friend, so refer to it often.

Place the pushrod length checker into a lifter and install a rocker arm assembly. Be sure the cam is rotated to the base circle. Seat the bottom of the adjuster screw up against the recess in the rocker arm and turn the adjuster screw clockwise one full turn down. This is the initial adjuster position. Adjust the pushrod length checker tool to the proper length, remove from the engine, and measure its overall length.

In every T&D rocker set is a small tool called a Stand Height Gage. When used per instructions, the stand height gage is invaluable for getting your rocker arms into their proper configuration. T&D also has available Pushrod Length Checkers. After the rockers are placed properly, you’ll need an accurate measurement to enable you to order correct length pushrods.

And, T&D also offers specialized tools to make your job of maintaining your valvetrain a breeze.

One answer to a question nearly everyone asks is, yes, even though T&D shaft-mount rocker arms are almost always “bolt-on,” the proper roller tip to valve relationship is critical. A little time and effort during assembly will reap huge benefits. In most cases, included shims will be adequate to reach proper alignment. T&D also builds custom height stands – many variations are on the shelf for immediate delivery. In extreme cases, machining the mounting pads on the cylinder head may be necessary. Never under any circumstances machine the mounting stands, grind reliefs into the rocker bodies, or modify the stands or rockers in any other ways.

Each rocker assembly is shipped with an instruction sheet that details just how to achieve optimum interaction between the roller tip of the rocker arm and the valve stem. We suggest that you familiarize yourself with that instruction sheet. If you cannot understand the basic instructions, please call or email our technical department.

We do offer a rocker inspection and rebuild service. Once we receive the rocker we check them in and put them out for inspection in the rebuild department.

The rockers are completely torn down except the roller tip, cleaned and the bearing bore is checked on a rod hone gage for roundness. When the rockers are originally honed, we know that they are perfectly round. If the bodies measure 0.001”+ out of round we now know that the rocker arm has had some sort of trauma in its life or it is at the
end of its cycle life. In either case, we recommend that the rocker body be replaced.

After the rocker body is checked, all of the rocker components and shafts are inspected under magnification. Parts showing signs of wear are marked an separated from the rest of the components and an inspection sheet is filled out. Once we receive the inspection sheet back the sales department goes over everything and then calls the customer back.

Please keep in mind the time frame on inspections varies depending on season.

We work very hard to keep the most common rocker sets on the shelf ready to ship. With so many different heads, offsets, ratios and options it is extremely difficult to keep every possible combination on the shelf.

• Shaft diameter is larger for large load carrying ability.
• Fully caged bearings for better wear and fewer bearing failures.
• Larger diameter adjuster for more material around the pushrod cup and better load carrying capability.
• We are very particular on geometry so every head has a specific part number to ensure that the rocker set fits with the least amount of work.
• More options, offsets and ratios.
• Custom rocker sets when needed.

When a cylinder head is assembled with the correct spring, retainer and keeper the tip of the valve protrudes past the top of the retainer. If a plus retainer and/or keeper is used, the valve tip becomes recessed in the retainer. The rocker arm will contact the retainer prior to the roller contacting the valve. To make the roller contact the valve tip, clearance must be cut into the rocker and can cause the rocker to break prematurely.

In the past we have seen and heard of some customers raising the stand to clear the spring, unfortunately this sacrifices geometry for clearance and can now lead to guide wear issues. The best fix for this issue is to eliminate the plus retainer and/or keeper or add a lash cap.

This is typically an issue with the small block Chevy, Ford and Mopar engines.

When a large diameter spring is used with a “low“ ratio rocker arm, it can create a clearance issue between the pushrod and the cylinder head. The large spring requires a longer rocker to keep proper clearances. The longer rocker requires the adjuster to be further away from the fulcrum, increasing the overall length of the rocker even more.

Some people machine the rocker arm for clearance, but this is NOT anything we recommend. The area of the rocker that makes contact with the

Spring diameter is a big factor mainly on small block Chevs, Fords and Mopars. Many engine builders stick with a relatively low ratio rocker arm and make up the lift with the cam lobe. The rocker arm itself is short so that if a 1.50 thru 1.60 ratio is used there is pushrod clearance. Because this rocker arm is “short” there is a limitation on the spring diameter that can be used. For 1.450” fulcrum length rockers the maximum spring diameter is a 1.550”. If the geometry is correct, the rocker will have plenty of clearance to the spring and retainer. If a 1.450” long rocker is hitting a 1.550” diameter spring and retainer combo, the usual reasons are the stand is too low or a plus height keeper or retainer have been used to increase installed height.

We have a limit on how much ratio we can fit on a particular rocker length and offset. We keep a nominal amount of material around that adjuster to be sure that the rocker lasts a very long time. In most cases the amount of offset the adjuster screw has is the biggest limiting factor. A rocker arm with zero offset is far more likely to be able to accept a high ratio then the same length body with a lot of offset.

The way we can fit a higher ratio in a rocker is building a rocker set that has a longer fulcrum length or in some cases going to a steel rocker option. With steel being stronger, the amount of material around the adjuster can be less. All factors are considered when selecting the correct rocker assembly and options for your combination.

T&D has always had internally oiled rocker arms. We prefer this method because you have pressurized engine oil being feed to the fulcrum of the rocker arm all the time. This improves bearing and shaft life.

Over the last 40 years we have experimented with many bearing types. We have found that a caged bearing lasts the longest. The cage between the needle rollers keeps everything in-line and rolling during the rockers back and forth motion. Full complement bearings will turn , lock up and skid for a moment each time the rocker arm changes direction, and this causes premature bearing and shaft wear.

When establishing geometry, we use a stand height gage. This gage allows you to establish the geometry quickly. The reason we use this gage is it is a known dimension. All of our gages are designed for a specific lift 0.550”, 0.650”, 0.750”, 0.850” and 1.000” lift. This number will be stamped right on the side on the gage.

This helps establish the tip to shaft relationship between the rocker arm and the valve. The two things that have an effect on this is lift at the valve and valve length. The valve length is the first thing you are compensating for when using the gage. Once the stand has been shimmed so that the shaft touches the gage, you will make a lift compensation. You will raise or lower the stand half the difference between the gage lift number and the actual lift at the valve. If you have greater lift than the gage you will lower the stand, if your lift is less than the gage you will raise the stand.

Example: If you had 0.700” gross lift at the valve and are using the 0.650” gage you would shim the stand to the gage and then remove 0.025” shim from under the stand to compensate for half the difference between 0.700” and 0.650”. If you have the opposite issue with the lift and gage you would raise the stand 0.025”. So if the gage was for 0.750” and gross lift is still 0.700” you would shim the stand till it touched, then raise it an additional 0.025”.

The reason we have you raise or lower the stand half the difference is it will split the roller tip travel on the valve stem over the full lift cycle.

If your stand is requiring more shim, then is supplied in the kit we typically have a taller stand to compensate for the extra height. The reason your stand may be that your head has a longer valve than what is typical for your specific head.

In some instances, we may have to build a custom stand for your head. When this is needed we will need you to use the stand height gage, put however much shim is required, make your lift compensation and give use the following information. The amount of shim that is now under the stand, the part number of the stand you are using and the placement of the roller on the stem compared to the centerline of the valve. With this information we will now know how to build the stand.

The main thing we are looking for in geometry is the pattern on the valve stem to ensure that valve guide wear is at a minimum.

The roller tip needs to start towards the intake port side of the head when the valve is closed. The rocker should then roll out to just past center towards the exhaust side of the head at half lift. Then from half lift to full lift, it should roll back to where it originated on the intake port side of the valve stem. The amount of tip travel will be directly affected by how much lift there is at the valve.

Example: If you have 0.550” lift, the roller tip should start 0.020-0.025” before centerline of the valve stem. If you had 0.650” lift, this pattern will roll back towards the intake side of the head and be 0.025-0.030”.

While a 210 radius pushrod may not be required in all applications most engine builders will use them anyway, just to make sure there is no chance of pushrod binding. The reason for the 210 radius pushrod is to gain clearance between the rocker arm adjuster cup and the pushrod a high lifts.